"Our goal was to investigate how a woman's menstrual cycle impacts consumption desires, product usage, and dollars spent within the food and beautification domains," study first author Gad Saad, a professor of marketing at the John Molson School of Business, said in a news release from Concordia University in Montreal.

In conducting the study, the researchers selected 59 women and asked them to keep detailed diaries on their beauty routine, clothing choices, calorie consumption and everything they bought over the course of 35 days.

The researchers also analyzed daily surveys the women answered on these topics, which asked them about their clothing choices and how long they spent grooming. The participants were also asked about activities such as sunbathing and eating high-calorie foods. The study revealed a distinct pattern in the women's behavior.

During the fertile phase of the women's menstrual cycles (roughly day eight to 15 of a 28-day cycle), the researchers found a significant increase in their focus on appearance. During their fertile days, women are also more likely to buy clothes, the study showed.

The study authors suggested that the explanation for this pattern of behavior can be traced back to women's evolutionary roots.

"In ancestral times, women had to focus more time on mating-related activities during the fertile phase of the menstrual cycle, when the likelihood of conception was highest," Saad explained in the news release. "Those same psychological and physiological mechanisms now lead women to engage in greater consumption of products relevant to reproductive drives during the fertile phase of their cycle."

Although food consumption among the women fell during their fertile days, the study revealed their appetites peaked in the luteal or infertile phase of their menstrual cycle (roughly day 16 to 28 of a 28-day cycle). The researchers noted the women's cravings for high-calorie foods spiked during this time, along with their food purchases.

"Women consume more calories during the luteal phase because they've evolved psychological and physiological mechanisms that favored non-mating-related activities like food foraging during the non-fertile phase of their cycles," noted Saad. "Different Darwin pulls, such as mating versus food, take precedence depending on a woman's menstrual status."

The study authors said their findings could shed light on these patterns of behavior and help women make more conscious decisions, which could affect their spending and eating habits.

"These consumption behaviors take place without women's conscious awareness of how hormonal fluctuations affect their choices as consumers," said Saad. "Our research helps highlight when women are most vulnerable to succumbing to cyclical temptations for high-calorie foods and appearance-enhancing products. These findings can help women to make choices for themselves contrary to the old canard of biological determinism."

A consumption-related smartphone app could help women track their daily shopping vulnerabilities by alerting them to certain high-risk days in their cycle, the study authors suggested.

The study was published recently in the Journal of Consumer Psychology.

More information

The U.S. Department of Health and Human Services has more about the menstrual cycle.